The benefits of regular aerobic exercise have been well established and accepted. However, due to time constraints, inclement weather, and other reasons, many people are prevented from aerobic activities such as walking, jogging, running, and swimming. In response, a variety of exercise equipment have been developed for aerobic activity. It is generally desirable to exercise a large number of different muscles over a significantly large range of motion so as to provide for balanced physical development, to maximize muscle length and flexibility, and to achieve optimum levels of aerobic exercise. A further advantageous characteristic of exercise equipment, is the ability to provide smooth and natural motion, thus avoiding significant jarring and straining that can damage both muscles and joints.
While various exercise systems are known in the prior art, these systems suffer from a variety of shortcomings that limit their benefits and/or include unnecessary risks and undesirable features. For example, stationary bicycles are a popular exercise system in the prior art, however this machine employs a sitting position which utilizes only a relatively small number of muscles, throughout a fairly limited range of motion. Cross-country skiing devices are also utilized by many people to simulate the gliding motion of cross-country skiing. While this device exercises more muscles than a stationary bicycle, the substantially flat shuffling foot motion provided thereby, limits the range of motion of some of the muscles being exercised. Another type of exercise device simulates stair climbing. These devices also exercise more muscles than do stationary bicycles, however, the rather limited range of up-and-down motion utilized does not exercise the user's leg muscles through a large range of motion. Treadmills are still a further type of exercise device in the prior art, and allow natural walking or jogging motions in a relatively limited area. A drawback of the treadmill, however, is that significant jarring of the hip, knee, ankle and other joints of the body may occur through use of this device.
A further limitation of a majority of exercise systems in the prior art, is that the systems are limited in the types of motions that they can produce, such as not being capable of producing elliptical motion. Exercise systems create elliptical motion, as referred to herein, when the path traveled by a user's feet while using the exercise system follows an arcuate or ellipse-shaped path of travel. Elliptical motion is much more natural and analogous to running, jogging, walking, etc., than the linear-type, back and forth motions produced by some prior art exercise equipment.
Exercise devices are also desirable which provide the additional advantage of being configured to provide arm and shoulder motions, as well as arcuate foot motions. Prior art devices utilizing arm and shoulder motions that are linked to foot motions incorporate forced coordinated motion, where the motions of a user's feet are linked to the motions of a user's arms and shoulders, so that one's feet are forced to move in response to the movement of one's arms and shoulders (in substantially an equal and opposite amount), and vice versa. Still other prior art devices limit the range of motions utilized by their systems, which can result in detrimental effects on a user's muscle flexibility and coordination due to the continued reliance on the small range motion produced by these exercise devices, as opposed to the wide range of natural motions that are experienced in activities such as running, walking, etc.
Despite the large number of exercise devices known in the prior art there is still a need for an exercise device which produces elliptical foot movement, and incorporates substantially related arm, shoulder, and rotational motions that are linked to the foot movements in a flexible and resilient manner. Exercise devices are desired that provides for a smooth stepping-running motion that prevents trauma to joints and muscles, while exercising a user's legs more fully than cycling or skiing devices. There is a continuing need for an exercise device that provides for smooth natural action, exercises a relatively large number of muscles through a large range of elliptical motion, employs arm, shoulder, and rotational movement, and allows for flexibly coordinated motion between the upper and lower body, i.e., motion that is substantially coordinated but still allows for some independent or uncoordinated motion between the movement of the user's feet.